Liquid ink printers, such as inkjet printers, place many small dots or drops of ink into very close proximity to each other on a print medium, such as plain paper, photo paper, etc. With little time to dry, different colored inks often bleed into each other on paper. Bleeding results from many factors including differing properties of different types of ink, such as pigment-based inks as compared to dye-based inks, as well as the type of media (such as photo paper or plain paper) onto which the ink is printed. Similarly, inks are carried in different vehicle formulations, such as non-reactive formulations and reactive formulations, which may include or omit salts, acids, or other additives. These differing properties affect many aspects of the appearance of each ink on the paper, such as edge quality, tone, etc. In one example, black inks and/or color inks are modified to be reactive, thereby causing a chemical reaction with each other as part of a bleed-reduction mechanism at a black-color interface.
Black-color bleeding results in color shift, ragged edges, as well as degradation of other print quality parameters. Maintaining optimal print quality (e.g. edge crispness, uniform tone, etc) for each color ink and for black inks is generally accomplished in different ways so that achieving optimal print quality for black text/objects may conflict with achieving optimal print quality for color text/objects. This conflict caused by different solutions for controlling ink/paper behavior has led to other hardware adaptations, such as maintaining separate sets of nozzles in printheads, one set for color and another set for black. In other words, one or more printheads have one orifice plate of nozzles for color inks and another separate orifice plate of nozzles for black inks. While this arrangement prevents cross-contamination of color and black inks at the nozzles, it also increases the complexity, size and cost of the printhead.
For these reasons, and many others, printers still face the challenge of placing color and black inks together on print media in a way that achieves optimal print quality for both the color ink and the black ink.